1. Field of the Invention
The present invention relates to plasma display panels including projections that are generated, along electrodes, on a surface of an insulation layer for covering the electrodes.
2. Description of the Related Art
An AC type plasma display panel includes a dielectric layer for covering display electrodes. The dielectric layer is formed on a substrate on which the display electrodes are arranged in a manner to extend over the entire screen. The dielectric layer that is made of low melting point glass, which is a general material, has a thickness of approximately 20 μm to 30 μm. A protection film is deposited on a surface of the dielectric layer. The protection film has a thickness of approximately 0.5 μm to 1 μm and serves to prevent sputtering due to discharges for the dielectric layer. Stated differently, the display electrodes are covered with a layered film including the dielectric layer and the protection film for a discharge gas space. The layered film including the dielectric layer and the protection film is herein referred to as an insulation layer.
A vapor deposition method (also called a vapor growth method) has recently received attention as a method for forming dielectric layers. Japanese unexamined patent publication No. 2000-21304 describes forming a dielectric layer made from silicon dioxide or organic silicon oxide using plasma CVD (Chemical Vapor Deposition) that is one kind of chemical vapor deposition method. The vapor deposition method enables provision of a thin dielectric layer having a uniform thickness. Further, the vapor deposition method makes it possible to form a dielectric layer with a low relative dielectric constant that is favorable to reduction of interelectrode capacitance at temperatures lower than a burning temperature of low melting point glass.
Layers obtained by the vapor deposition method have a structural feature in which a surface is uneven due to reflection of irregularities of a foundation surface (a surface on which layers are formed). More specifically, surfaces of layers obtained by the vapor deposition method are not even unlike a surface of a low melting point glass layer that is burned at sufficiently high temperatures. A dielectric layer is formed on a substrate on which display electrodes are arranged. Accordingly, a dielectric layer obtained by the vapor deposition method has an uneven surface in which portions corresponding to the display electrodes bulge out compared to the other portions by amounts corresponding to the thickness of the display electrodes. Since a protection film formed on the uneven surface is sufficiently thin, the surface of the protection film, i.e., a surface of an insulation layer is similarly uneven.
In a surface discharge AC type plasma display panel suitable for color picture display, partitions as discharge barriers are arranged on a second substrate that faces a first substrate on which display electrodes and an insulation layer are arranged. Partition arrangement patterns include a stripe pattern in which a discharge gas space is divided on a column basis of a screen and a mesh pattern in which a discharge gas space is divided on a cell basis of a screen.
The insulation layer abuts against the tops of the partitions within the plasma display panel of this type. In a state where the insulation layer abuts against the tops of the partitions, the partitions serve to prevent discharge interference among cells and function as spacers for equalizing a thickness (a dimension in the facing direction of substrates) of the discharge gas space within the screen.
Japanese unexamined patent publication No. 2000-21304 describes a structure in which projections of an insulation layer formed on a first substrate abut against a stripe-patterned partition supported by a second substrate. Further, Japanese unexamined patent publication No. 2003-308784 describes a structure in which projections of an insulation layer abut against a mesh-patterned partition.
In plasma display panels including projections that are generated, along display electrodes, on an insulation layer for covering the display electrodes, a problem arises that gaps exist between partitions and parts other than the projections in the insulation layer and discharge interference is apt to occur among adjacent cells, compared to the case of plasma display panels having an insulation layer with a flat surface.